The present invention relates generally to cutting inserts and cutting tools and, more particularly, to double-sided cutting inserts.
In designing, cutting inserts, it is typically desirable to provide the cutting insert with the maximum number of usable cutting edges possible so that the insert can be indexed to different positions to permit use of a new cutting edge when an edge is worn or broken. Inserts are typically mounted to toolholders by means such as clamping screws or bolts, and many current designs permit an insert to be indexed by turning the insert around the bolt so that a fresh cutting edge is moved to a working position. In addition, many current designs are of “double-sided” inserts that permit the insert to be flipped over so that the insert can be indexed around the screw or bolt, such as is shown in U.S. Pat. No. 7,241,082.
When making smaller inserts intended to be used to machine smaller items or shapes, it becomes increasingly difficult to make indexable inserts without compromising the strength of the insert or the ability to provide sufficient surface space on the insert, for mounting of the insert against abutment surfaces on a toolholder. It is necessary to provide a hole through the insert for the mounting screw or bolt and, particularly in the case of double-sided cutting inserts, as insert size becomes smaller, a trade-off must often he made between providing a smaller, more fragile screw or bolt or a more fragile insert that has only minimal insert material between the hole and working surfaces of the insert.
It is desirable to provide a cutting insert and cutting tool that facilitates providing a hole of maximum size in an insert while still providing substantial strength to the insert.
According to an aspect of the present invention, a double-sided cutting insert comprises two identical opposing end surfaces, each end surface having four corners, a peripheral side surface extending between the opposing end surfaces, the peripheral side surface comprising two opposing identical major side surfaces, four spaced apart major cutting edges, each major cutting edge being formed at an intersection of each major side surface with each end surface, and a hole extending through the insert from one of the major side surfaces to the other of the major side surfaces, wherein each end surface comprising major rake surfaces adjacent the major cutting edges that form first angles with planes of the major side surfaces, and a central support surface forming a second angle with the planes of the major side surfaces, and each end surface comprises major intermediate surfaces between the major rake surfaces and the central support surface, the major intermediate surfaces forming third angles with the planes of the major side surfaces that are greater than the first angles and smaller than the second angles when measured in a central plane that extends along a central axis of the hole and is generally perpendicular to the planes of the major side surfaces and planes of the central support surfaces.
A cutting tool according to an aspect of the invention includes a double-sided cutting insert as described above in combination with a toolholder comprising a body and a pocket formed in the body for receiving the cutting insert, the pocket comprising major side and central support abutment surfaces for abutting against respective ones of the major side surfaces and one of the central support surfaces.